The technical field of the invention is that of methods and devices for manipulating dielectric or metal microparticles or nanoparticles, or organic particles such as molecules, microorganisms, or viruses.
These methods and devices are used, for example, in microfluidic devices or in labs-on-a-chip for analysis or chemical or biological synthesis applications.
Methods for trapping and moving particles in a fluid are known from the prior art and are commonly called “optical tweezers.”
These methods use a focused laser beam to trap and manipulate a particle contained in a fluid.
The refraction of light at the interface between the particle and the surrounding fluid exerts a force on the particle, a function of the difference in refractive index between the particle and the fluid, which allows manipulating the particle (for example see Ashkin et al., Optics Letters Vol. 11, p 288 (1986)).
The force exerted on the particle is a function of the electric field gradient of the laser which displaces the particle toward the most intense area of illumination in the center of the focused beam, the focal area of the focused laser beam thus constituting an “optical trap.”
Document U.S. Pat. No. 7,732,758 B2 describes an example of such an optical trap in which a focused laser allows holding, manipulating, and moving a particle in a fluid.
The force exerted by the laser beam on a particle is particularly dependent on the composition and size of the particles. It is therefore possible to sort particles according to these parameters, and there is a need for devices for trapping, moving, and sorting particles that can trap, move, and sort a large number of particles for the microfluidic and lab-on-a-chip applications mentioned above.
The device described in U.S. Pat. No. 7,732,758 B2 has the disadvantage of using one laser generator per optical trap and thus only allows trapping and manipulating a small number of particles unless a device of great complexity and size is implemented.
Document U.S. Pat. No. 7,973,275 B2 describes an example of a method for trapping and moving particles that manipulates particles by means of multiple optical traps generated by a single laser source.
This device, however, requires the use of an active optical element controlled by a computer in order to generate a hologram. The presence of such an active optical element makes such devices expensive and complex to use. In addition, the determination of the holographic figure to be projected requires significant computing power, and some optical trap configurations are impossible to generate.
The present invention is intended to overcome these disadvantages.